1. Field of the Invention
The present invention relates to surface coatings having high durability and showing good wet-lubricity; methods for surface coating; and medical devices having the same.
2. Related Background Art
Hitherto, surface coatings having wet-lubricity have been applied to medical devices having parts which are brought into contact with living bodies in various methods, in order to reduce pain and injury to the living bodies. However, since these surface coatings having the wet-lubricity generally have low affinity for materials forming medical devices, they have disadvantages that they dissolve or are peeled off in living bodies.
For improving this, there is, for example, a method in which a material surface is treated with ozone to generate functional groups on the substrate surface, followed by graft-polymerization of s hydrophilic polymer onto the substrate, as disclosed in Japanese Unexamined Patent Application Publication No. 5-76590; or a method performing a plasma treatment, as disclosed in Japanese Unexamined Patent Application Publication No. 5-168695. The methods, however are not so preferable because they have side effects such that durability is low and mechanical properties of the substrate are lowered.
Also, as disclosed in Japanese Unexamined Patent Application Publication No. 8-33704, a method in which a polymerization of a monomer is performed in the presence of a hydrophilic polymer compound to produce a second polymer compound, and an interpenetrating mesh structure of the two kinds of the polymer compounds is formed on a substrate surface, has been proposed, but the method has disadvantages that the substrate is deteriorated, and remaining monomers and oligomers elute.
Further, a method in which hydrophilic polymer is blended with a urethane resin having adhesion with a substrate, as disclosed in Japanese Unexamined Patent Application Publication No. 11-22613; and a method in which a urethane resin having a hydrophilic backbone is used, as disclosed in National Publication of International Patent Application No. 11-506375, have an issue to be solved that the adhesion with a substrate or wet-lubricity is not satisfied, though the lowering of the physical properties of substrates can be avoided. As a method for immobilizing a water-soluble polymer substrate on a substrate surface using an isocyanate group-containing compound, a method in which a solution including an isocyanate group-containing compound is coated, followed by binding a water-soluble polymer substance, as shown in Japanese Unexamined Patent Application Publication No. 60-259269; and a method in which a substrate is coated with a hydrophilic polymer whose terminals are isocyanated with a thermally decomposable blocked isocyanate, as shown in Japanese Unexamined Patent Application Publication No. 10-231347 are proposed. According to these methods, however, sufficient durability and lubricity cannot be obtained yet. In addition, as shown in U.S. Pat. No. 4,487,808, they are not suitable for use in medical devices whose substrate is thin and whose mechanical properties are remarkably changed due to heat history, such as, particularly, balloon catheters, because a heat treatment is required to immobilize the isocyanate group-containing compound to be coated, and the like. Also, substrates having no active hydrogen on their surfaces have insufficient durability, too.
In order to overcome the disadvantages, as disclosed in Japanese Unexamined Patent Application Publication No. 2003-225301, a method in which a substrate is swollen with a solvent, with which a urethane resin is acted, is proposed. Even this method has a disadvantage that the substrates are restricted, and mechanical properties of the substrate are affected.